Body electrode assembly



United States Patent 72| Inventor RleltardMJermln Dreshenlennsylvania|2l| Appl No 655,508 [22] Filed JI|24,1967 l45| Patented Dec.8,l970 l lAsatgnee Gnltonlndustrmlnc.

acorporationofbelaware I54] BODY ELECTRODE ASSEMBLY7Clalms,5l)rawlngl"igs.

I52] U.S.Cl. RUIZ-06. 339/105 [5H lnt.CI. A6lb5/04 smFieldofSearch.............. 174173. 9; 339/l05; 128/2 06(El. 21.404.4IO.4! I 4l6. 4l7.4l8.(Digest4l I56] RefereneesCited UNITED STATES PATENTS877.383 lll908 Swan. 339/[05 l.989.282 Ill935 Kimbleetal..... 128/416.170.459 2/1965 Phippsetal. l28/2.06 1295.5 "1967 Kahn. i28/2.063.340.868 9/1967 Darling l28/2.06 3.420123 lll969 Day et l28/2.06

Primary Examiner-William E. Kamm Anomey- Wallenstein, Spangenberg,l-lattis & Strampel ABSTRACT: The electrode assembly of the inventionmost advantageously comprises an electrode housing made of moldedinsulating material and having a base portion with a skin-contactingsurface interrupted by a conductive pastereceiving recess locatedcompletely within the margins of said skin-contacting surface Thehousing has a head portion with a cavity therein intersecting the recessin the base portion thereof A conductive electrode-fonning; disk closesthe opening between the recess in the base portion of the housing andthe cavity in the head portion thereof. An insulated signal lead extendsthrough the head portion of the housing and said cavity therein 'andthen bends tightly back into the housing around two corners where theends of the signal lead terminate in the cavity in the head portion ofthe housing. The conductor of c the signal lead is soldered to theelectrode-forming disk and the cavity is filled with an encapsulationmaterial. To apply the electrode assembly. the paste-receiving recess inthe housing is filled with a conductive paste and the electrode assemblyis placed upon the patients skin and secured and sealed thereto by apatch of cushioning material which envelopes the housing. The patch hasa pressure sensitive adhesive layer which holds the patch tightly aroundthe electrode housing and prevents any drying of the paste from theelectrode assembly.

3 8 2| (3 82 Rid-mm: MBERM I- YEA/TOR connect such equipment aselectrocardiogram, electroencephalogram, electroocculogr'am andelectromyogram equip ment to a skin surface. n

Until recently, medical electronic equipment for diagnostic ortherapeutic purposes has been of the nonportable variety where thepatient being tested or treated is confined to the hospital or doctorsoffice because of the size and weight of the measuring or treatingequipmentinvolved; Generally, the electrodes connected to the equipmentare applied to the patient for a relativelyshort period of time whilethe patient is maintained relatively immobile. However, recentlyminiaturized electronic medical equipment has been developedwhich is solight in weight that it can be carried on the patient so that measuringor treatment procedures can be carried out for a long period of time atlocations away from the hospital or doctors office and while the patientis performing his normal routine work or bodily exercises. For example,portable electrocardiogram equipment of this type is now availablepermitting dynamic electrocardiograms to be taken off the patient whilehis is engaged in his normal physical activities. However, the use ofthe portable electromedical equipment referred to imposes many severerequirements upon the body connecting electrodes. Thus, the electrodesmust be small and light-in-weight and must also be held securely inplace and make continuous very low resistance contact with a givenlocation of the body'to which it is applied while the patient isperforming a variety of movements. Also, the leads extending to theelectrodes must be such that they can withstand appreciable pullingforces without breakage.

The body electrodes heretofore developed proved unsatisfactory and lessthan ideal because they failed to satisfy one'or more of theaforementioned objectives. Perhaps one of the most significantdeficiencies inthe electrodes heretofore developed was their inabilityto withstand repeated large pulling forces on the leads extending to theelectrodes without breakage. As will appear, the preferred form of thepresent invention satisfies all of the aforementioned objectives.

In accordance with one of the features of the invention, the leadextending to each electrode is connected to the electrode housing in amanner where the strain placed on the lead is relievedfrom the point ofconnection of the lead to the electrode in a very simple and inexpensivemanner. i

In the most preferred form of the invention, the electrode includes arelatively thin molded housing body preferably having a relatively widebase portion and a relatively narrow upper or head portion. The smalloverall thicknessof the housing makes it comfortable for application tothe skin and adaptable to all skin surface irregularities. The headportion of the housing preferably has a cavity provided with avoltagereceiving electrode surface to which is fed the skin voltage in ameasuring application or the applied current or voltage in a treatingapplication. The signal lead, which comprises an inner conductor and'anouter insulating sleeve, passes through a passageway extendingcompletely through the head portion of the housing and intersecting theaforementioned cavity. The signal lead passes through this housingpassageway and cavity and bends snugly around a corner of the housing atthe periphery thereof, then bends snugly around another corner and thenreenters the housing and passes through a second passageway which alsointersects the aforesaid cavity. The end of the signal lead conductor islocated in the housing cavity where it is stripped of insulation andconnected by soldering or otherwise to the aforementionedvoltage-receiving electrode surface within the cavity of the housing.Means are provided in the cavity for immovably anchoring the spacedportions of the signal lead which pass into the cavity. This means mostadvantageously is an encapsulation material, such as an epoxy resin,which fills the cavity and immovably anchors the signal lead and sealsthe bared end portion of the signal lead conductor. With thisconstruction, longitudinal pulling forces applied to the signal lead issubstantially eliminated at the FIG. 3 taken along section line 4-4; and

point of connection of the bare end of the signal lead conductor to theelectrode surface: in the housing cavity.

In accordance with another feature of the invention, the base portion ofthe electrode housing has a flat skin-contacting surface which isinterrupted by a conductive paste-receiving recess or well locatedwithin all of the margins of the skin contacting surface of the housingwhich aids in sealing or closing the recess on all sides so that aconductive paste placed in the recess will normally be trapped' betweenthe skin and the defining walls of the recess. To ensure theretension ofthe paste, an auxiliary seal is formed around the periphery of therecess so that none of the paste can escape by evaporation or otherwisefrom the electrode. This auxiliary seal is most advantageously providedby a cushioning, anchoring and sealing pad which may comprise a body ofresilient compressible material having a pressure sensitive adhesive onone side thereof, the pad having an area much greater than the electrode housing so the pad while enveloping the electrode housing can bepressed against the portion of the skin surrounding the electrodehousing toanchor and seal the same to the skin.

The paste-receiving recess and said housing cavity are mostadvantageously separated by a silver disc or pellet whose outer surfaceconstitutes the electrode surface to which the signal lead conductor ispreferably soldered. The design and arrangement of the silver disc,conductive paste-receiving recess and adhesive-coated cushioning padallows for large variations in pressure against the electrode withoutcausing distortion of the electrical signal being sensed. This isimportant when clothing is present over the electrode and/or the subjectpresses on or lies on top of the electrode.

The above and other advantages and features of the invention will becomeapparent upon making reference to the specification to follow, theclaims and the drawings wherein:

' FIG. 1 is a top perspective viewof an electrode assembly incorporatingfeatures of the presentinvention;

FIG. 2 is a bottom perspective view of the electrode assembly shown inFIG. 1;

FIG. 3 is an enlarged, partly broken away top view of the electrodeassembly of FIGS. 1 and 2;

FIG. 4 is a sectional view through the electrode assembly of FIG. 5 is abroken away perspective view of the electrode assembly applied to theskin surface ofa patient with conductive paste in the electrode-housingrecess.

Referring now to the drawings, the electrode assembly there illustratedand identified by reference numeral! includes an outer housing 2 ofgenerally circular cross section form which a signal lead 3 extends. Thesignal lead comprises a relatively small conductor 3a and a surroundinginsulating sleeve 3b which may be Teflon tubing which has been shrunksnugly around the conductor. The housing 2 may be a molded body made ofany suitable material, such as a transparent synthetic plastic material.The exemplary housing has a relatively wide base portion 2a with a flatannular skin-engaging surface 6. The surface 6 is interrupted by acentered paste-receiving recess 8 which tapers inwardly of the housingand intersects and axially centered cavity 10 formed in a reduced headportion 2b of the housing. The illustrated cavity 10 is of cylindricalshape and of somewhat larger diameter than the inner narrow end of therecess 9, thereby providing an annular shoulder or ledge 12 on which ismounted an electrode-forming disc or pellet 13 which most advantageouslyis. made of a highly conductive silver-chloride composition. Theelectrode-forming disc 13 may be adhesively secured to the ledge 12 by asuitable cement or may be held in the cavity by encapsulation material15 filling the cavity 10 which may be an epoxy resin. The disc 13occupies only a small portion of the cavity 10 to provide space for thepassage of the signal lead 3.

The head portion 2b of the electrode housing is provided with a firstpassageway I4preferably extending diametrically through the entirehousing in a plane adjacent to the electrode-forming disc 13 andintersecting the cavity 10 which breaks the passageway 14 into twodiametrically separated sections. The signal lead 3 passes through thepassageway 14 where it bends tightly around a corner 16 at the end ofthe passageway 14 and .then extends circumferentially a small distancearound the outside of the housing where it bends tightly around a corner18 at theend of a second passageway 20 which extends in about the sameplane as the passageway 14 through the housing wall to intersect thecavity 10 adjacent the electrode-forming disc 13. The end of theconductor 3a of the signal lead 3 within the cavity 10 is bared andsoldered or otherwise electrically and physically attached at 17 to theelectrode-forming disc 13. The spaced portions of the signal lead 3within the cavity l are immovably anchored with respect to the housing 2by means of encapsulating material 15 which is poured iii liquid form inthe cavity and allowed to harden.

As best shown in FIG. 5, when the electrode assembly is applied to apatients skin, the recess 8 between the patients skin and theelectrode-.formingdisc 13 which seals off one end of the recess 8 isfilled with a'conductive paste 21 which forms a low resistance pathbetween the surface of the patients skin 23 and the electrode-formingdisc 13. The electrode assembly is fixedly attached to the patients skinby suitable means, most preferably a flexible and resilient cushioningpatch 25 which is preferably of much larger diameter and thickness thanthe electrode assembly housing and may be made of a closed cell foammaterial like polyurethane or the like. The inner surface of the patch25 is coated with a layer 27 of pressure-sensitive adhesive material,which readily sticks to the skin surface 23. When the patch 25 envelopesthe electrode assembly and is pressed securely around the housing 2thereof, the assembly is securely held in place and a continuous seal isformed around the housing which prevents the evaporated or fluid pastefrom escapingfrom 'the electrode assembly.

It should be appreciated that the various features of the presentinvention provide a very simple and inexpensive body electrode assemblywhich provides a very convenient sealed recess fora conductive paste sothat a low resistance, long lasting connection is maintained between thepatients skin and the electrode-forming disc 13. Moreover, any pullingforce applied to the signal lead 3 is relieved from the solderconnection at 17 because of the snug reverse bending of the signal leadaround the comers 16 and 18 and the manner in which the signal lead isanchored to the housing 2 by the encapsulation material 15. Aspreviously indicated, the invention allows for large variationsinpressure against the electrode without causing distortion of theelectrical signal being sensed. This is important when clothing ispresent over the electrode and/or the subject presses on or lies on topof the electrode. Also, the electrode assembly is of a permanentreusable construction and is easily cleaned and refilled with paste.

It should be understood that numerous modifications may be made in themost preferred form of the invention described above without deviatingfrom the broader aspects thereof.

I claim:

1. An electrode assembly for picking up or delivering small electricalsignals from or to a skin surface, said electrode assembly comprising: ahousing having a skin-contacting surface on the inner side thereof, acavity containing an externally exposed conductiveelectrode-formingmeans to which a voltage is to be applied, a first passageway extendinggenerally parallel to said skin-contacting'surface, a second passagewayextending generally parallel to said skin-contacting surface andintersecting said cavity, and an outwardly facing surface extendingbetween the ends of said passageways remote from said cavity andformingcorners at'the intersection of said outwardly facing surfaceandsaid passageways; a signal lead for connecting said electrode-forming,means in said housing to an external device, said signal lead having aninner end section passing through said first passageway in said housing,then along said outwardly facing surface of the housing and through saidsecond passageway thereof. to terminate in said cavity, the signal leadtightly vending around said corners, the end of said signal lead beingelectrically connected to said electrodeforming means in said cavity;and means for immovably anchoring said inner end section of said signallead to said housing so the signal lead to said housing so the signallead remains tightly bent around said housing corners.

2. The electrode assembly of claim 1 wherein said first passageway alsointersects said cavity so portions of said signal lead ahead of andbeyond said housing corners pass into said cavity, and said anchoringmeans isa body of encapsulation material in the cavity which embeds saidportions of the signal lead located in the cavity.

3. The electrode assembly of claim 1 wherein said housing has a hollowbase portion including a recess and a hollow head portion containingsaid cavity communicating with said recess and opening onto the outerside of the housing, said conductive electrode-forming means in saidcavity being a conductive disc mounted in said cavity so as to seal-offthe opening between said recess and cavity, said signal lead iselectrically connected and physically attached to the outer side of saiddisc and extends to the outside of said housing, and a body ofencapsulation material in such housing cavity which seals andencapsulates the outer side of said disc and the portions of the signallead passing into said cavity.

4. An electrode assembly for picking up or feeding electrical signalsfrom or to a skin surface, said electrode assembly comprising: an outerhousing havinga skin-contacting surface on the inner side thereofadapted to be placed on the skin surface, a voltage-receiving electrodein said housing, a signal lead extending to said housing andelectrically connected to said electrode, said housing surface beinginterrupted by a conductive paste-receiving recess located within allthe margins of said surface and defined by inner walls of the housingwhich seal said recess on all sides but the side facing theskincontacting side of the housing, so a conductive paste placed in therecess is held betweenthe skin'and the housing, said voltage-receiving,electrode being at least part of one of the defining walls of saidrecess, a body of cushioning material for isolating the housing fromexternal forces on the side of said housing opposite the side containingsaid recess, said body of cushioning material being a separate piece ofmaterial which extends over an area much larger than that encompassed bysaid electrode housing to envelope all exposed sides of the housing, andsaid piece of cushioning material having a pressure sensitive adhesivelayer on the inner side thereof for contact with the users skin along acontinuous ring around said electrode housing.

5. An electrode assembly for picking up or feeding electrical signalsfrom or to a skin surface, said electrode assembly comprising: and outerhousing having a skin-contacting surface on the inner side thereofadapted to be placed on the skin.

surface; a signal lead extending to said housing and including an innerconductor surrounded by an insulating sleeve which terminates short ofthe end of the conductor to expose the end of the conductor; saidhousing surface being interrupted by a conductive paste-receiving recesslocated within all the margins of said surface and defined by innerwalls of the housing which seal said recess on all sides but the sidefacing the skincontacting side of the housing, so a conductive pasteplaced in the recess is held between the skin and the housing; saidhousing being provided with a cavity; a voltage-receiving electrodewhich forms a wall between said cavity and recess; a first passagewaywhich passes completely through the housing from one side to the otherand intersects said cavity and a second passageway extending from theoutside of the housing to said cavity; said signal lead passing throughsaid first passageway andsaid cavity and after leaving said firstpassageway passing along the outside of said housing and then bendingback into the housing where it enters said cavity through said secondpassageway; and said exposed end of said signal lead conductor overlyingsaid electrode and attached thereto within said cavity.

6. The electrode assembly of claim 7 wherein the portion of the signallead which extends into said first passageway and 3 ,5 45 ,432 l p 5 g6' passes through said cavity is anchored in saidcavity by a body 7. Theelectrode assembly of claim SWherein there is proof encapsulationmaterial embedding both the latter portion of vided means for anchoringthe 1 portion of said signal lead the signal lead and the exposed end ofthe conductor thereof. passing through said first passageway and!entering said cavity.

